There is no question that the Jets defense caused a lot of excitement in 2009. Under the leadership of head coach Rex Ryan the defense transformed itself from a very passive unit to the most aggressive unit in the NFL. The Jets led the NFL in almost every important statistical category. They allowed the least points and least yards per game. Their pass defense was number one by a wide margin and the team allowed less than 14 points in half of their regular season games. The defense, which already featured the best player in the league in cornerback Darrelle Revis only looks to have improved by adding CB Antonio Cromartie and LB Jason Taylor to the mix. Needless to say the fan base can not wait to see this unit take the field in 2010 and dominate the league en route to a championship run.

However, a comment was made by Football Outsiders a few months ago questioning whether or not the defense had the ability to duplicate the success of 2009 in 2010. The basic premise was that a team with the number 1 defense, based on the FO metrics. usually falls back to the pack the following year. I wanted to take it a step further and look into the trends not just of the number 1 defense, but of the teams that had traditionally been considered defensive powerhouses, or simply fielded some very high ranking teams, in the last decade. I used my own defensive efficiency ratings to research the teams. These rankings simply measure the percentage that a defense holds a team below their scoring average. For example, a team allowing 17 points a game against a schedule that on average scores 20 points a game would be credited with a 15% efficiency rating.

Just How Good was the 2009 Jets Defense?

There was a thought floating around followers of the team that the Jets defense was very good, but not great. This thought was supported by the lack of a pass rusher and the defense’s late game implosions against the Jacksonville Jaguars, Atlanta Falcons, and Miami Dolphins. Even the head coach at one point said he expected the defense to be better. However, the Jets efficiency rating of 32.39% ranked 9th in the decade and clearly would be considered an elite defense. The following teams ranked above a 30% during the 2000’s:

Just a quick glance at that list shows a scary trend- it takes a very long time for a defense to reach elite status a second time, if they ever do it at all. It took the Ravens six years, the Bears four years and the Titans eight years to get the defense back to a 30% rating. The other squads never returned. So based on the historical data its more likely that the Jets defensive performance was a highlight performance rather than the starting point of the next 1985 Chicago Bears.

Just How Drastic Are the Defensive Falls?

Its been pretty huge. The following chart shows the percentage decrease of the elite level defensive teams the following season.

The lowest fall was the 2003 Eagles who were down 38.6% from their 2002 high. If the Jets matched that they would fall to a 19.89% efficiency rating. To put that number in perspective the Jets would have allowed about 3 points per game more last year with that efficiency rating. That would still be top 5 in the NFL, but no longer number 1 and no longer the type of defense that carries a team to a title.
Most of the drops have been much more drastic than that of the Eagles. Four of the teams posted negative efficiencies following their elite level runs, meaning they went from fielding one of the best defenses of the decade to a below average defense the following year. The normal drop is more than 50%, which would leave the Jets well under expectations if it were to happen.

Can the Jets possibly have been a one hit wonder?

This is another cause for alarm. The Jets in 2008 trended as a below average defense under Eric Mangini, posting a -5.53% rating, so the defensive turnaround was gigantic last year. This was not the first time the Jets made a large jump. The Jets 2003 squad was a slightly above average 4.18% and rapidly trending downward when out of nowhere the 2004 team posted a excellent 25.82%. Much of the credit went to the additions of rookie MLB Jon Vilma and defensive coordinator Donnie Henderson. The fans fell in love with the defense, the coaches, and every move the team made. Needless to say they went right back down in 2005 falling to a -6.71% and never coming close to the 2004 level in the next four seasons.

Of the eight teams that truly came out of nowhere to jump into the 25%+ category, six of them fell back to average or below average the next year. The exceptions were the 2008 Colts, who only fell to a 14.79%, and the 2006 Bears that fell from a 35.48% to 17.95%. Hopefully the Jets follow the examples of those two squads in 2010, but history shows teams with no track record of playing great defense often go back to playing mediocre defense.

Assuming the best, what looks to be a sustainable level?

Lets look at a chart with all of the good defensive teams of the decade to see how they trended.

The chart is messy, but the really good defense looks to be able to sustain performance close to 20% in most seasons. The Ravens, who are the team the Jets most get compared to, had 5 seasons above a 20% and have been well above 20% in three of the last four seasons. The Steelers are right there with the Ravens with 5 seasons of really great defensive football and the Patriots posted 4 seasons above 20%. On the flip side is the Titans and Bears model of teams who put up awesome years every few seasons and surround them with very mediocre years. But if the coach has really turned the Jets into a good defensive team we can expect to have a defense that is almost always above average and a few years where it all clicks and the defense plays at a very high level.

Is there any hope for a repeat performance?

There are a few things to look at it that could bring some hope for next season, even though no other team has been able to do it. One is the hunger factor. The 2000 Ravens, 2002 Buccaneers, 2004 Patriots and 2008 Steelers all went to the Super Bowl which may have led to the big drops the following years. Teams in the NFL are often accused of going through the motions after Super Bowl years and the Jets did not reach that level last year.

Secondly, the only elite defensive team who, on paper, faced a tougher offensive schedule than the 2009 Jets were the 2002 Bucs. The Jets opponents in 2009 averaged 21.81 PPG while the Bucs opponents averaged 22.59 PPG, so you could make an argument that the Jets were more legitimate than other great defenses that faced easy schedules. The elite teams that saw their schedules get easier the following season are the teams that saw the least decrease in the defensive efficiency. On paper the Jets look to have a schedule that is about equivalent to last years, which should be a good sign to limit the fall.

So what is the conclusion?

For the Jets to repeat the kind of performance they had last season will require the Jets to do something that no other team has been able to
do in the last 10 years. The best case scenario is to field a team that is going to rank somewhere around 4th in the NFL in defense and it should not be a shock if the defense falls out of the top 5 entirely.
I think this puts things in a much clearer light about why the Jets were so insistent about changing things up on defense by removing Kerry Rhodes and brining in Taylor, Cromartie and Kyle Wilson. I think it also is a major reason why the Jets spent a great deal of the offseason loading up offensive firepower and planning on a more pass oriented offense rather than the much talked about “Ground and Pound” philosophy that the team drilled into our heads last year. The odds of the Jets being able to win 17-14 with a Trent Dilfer type offense simply were not good enough to expect the team to run the same system as last year.
For the Jets to return to the AFC Championship game this year it seems as if the offense is going to have to be far more explosive and make up for a few defensive letdowns in 2010.